Gummy smile: causes and treatment, from botulinum toxin to surgical crown lengthening

What is a gummy smile and from how many millimetres is it diagnosed?

A gummy smile, or excessive gingival display, is when a full smile shows clearly more gum above the upper incisors than usual. There is no single agreed threshold: a review by Maleki et al. (2024) uses more than 2 mm, a review by Mercado-García et al. (2021) more than 3 mm, and in some European countries up to 4 mm is considered acceptable.

In practice, a smile is usually called gummy when more than about 3 to 4 mm of gum shows. Mercado-García et al. describe it as a non-pathological condition that disrupts the harmony of the smile. Treatment is therefore the patient’s aesthetic decision, not a medical necessity.

How common it is depends on the threshold used. Older studies cited in the 2021 review report 10.5 to 29% of young adults, more often women, and a study by Tatakis et al. (2024) among adults in the USA 6.9%. It can therefore be assumed to affect roughly one person in ten to one in fifteen or so.

What causes a gummy smile?

A gummy smile has several possible causes, related to the lip, to the gums and teeth, or to the structure of the upper jaw, and in many people the causes combine. A review by Maleki et al. (2024) lists six main ones.

A combination of causes is common. In a study by Andijani and Tatakis (2019) of 56 people seeking treatment, an overactive lip alone accounted for 45.3% of cases, altered passive eruption alone for 20.8%, and both causes together for 34%. When 4 mm of gum or more was showing, an overactive lip played a part in 95% of cases.

• An overactive upper lip: the muscles that raise the lip pull it higher than usual when you smile.
• A short upper lip or a short philtrum (the groove between the nose and the upper lip).
• Altered passive eruption: after the teeth came through, the gum and bone did not recede to the usual level, so part of the crown stays covered and the teeth look short.
• Gum overgrowth, that is enlargement of the gum tissue itself.
• Overerupted upper incisors, often with a deep bite.
• Vertical maxillary excess, a problem in the structure of the bone in which the upper jaw has grown too much vertically.

How does a dentist establish the cause of a gummy smile?

The cause of a gummy smile is established during an examination, and the choice of method depends on it: the same amount of visible gum may need completely different treatment in two people. The dentist measures how much gum shows at rest and in a full smile, assesses the length and proportions of the tooth crowns, and the length and mobility of the upper lip.

When altered passive eruption is suspected, what matters is the position of the gum margin and the bone relative to the junction between enamel and root, that is whether part of the crown is still hidden under the gum. The dentist also assesses the condition of the gums, the bite and the structure of the upper jaw, because gum overgrowth, protruding incisors and excess bone in the upper jaw need a different approach from an overactive lip alone.

If there are several causes, the plan may combine methods, for example a gum procedure with botulinum toxin, or orthodontic treatment with a surgical procedure. Before deciding, it is worth asking which cause each proposed method addresses and how long its effect lasts.

Gummy smile treatment: the methods compared

Treatment for a gummy smile is matched to the cause, not to the number of millimetres alone. A review by Tatakis and Silva (2023) assigns aesthetic crown lengthening to altered passive eruption and lip repositioning to an overactive lip; according to a review by Rojo-Sanchis et al. (2023), orthognathic surgery is the treatment of choice for vertical maxillary excess.

The review by Maleki et al. concludes that surgical methods give a more lasting effect in more severe cases, while non-surgical methods help in mild ones, but their effect fades over time. The table sets out the options described in studies.

Botox for a gummy smile: how it works, how long it lasts and why it is off-label

Botulinum toxin, commonly called Botox, weakens the muscles that raise the upper lip for a few months, so the lip lifts less when you smile and covers more of the gum. A meta-analysis of 17 studies by Zengiski et al. (2022) reports that the amount of visible gum fell by an average of 3.42 mm after 2 weeks, the effect lasted at least 12 weeks, and after about 24 weeks it was close to the starting point.

The method works best for a gummy smile of up to about 4 mm caused by an overactive lip, and it changes neither the gum nor the teeth. In practice the effect usually lasts a few months, about 3 to 6, and the treatment has to be repeated to maintain it. Older reviews note that the evidence is limited and of low quality, and an analysis by Chagas et al. (2018) judged the data on duration of effect to be scarce.

Treating a gummy smile with botulinum toxin is a use outside the licensed indications (off-label). The summaries of product characteristics of the products available in Poland, such as Botox, Dysport or Bocouture, do not list gummy smile among their indications, which means that this use has not been approved in the medicine’s authorisation process. A doctor who proposes it should say so before the procedure.

All botulinum toxin products in Poland are prescription-only medicines. In a statement of 14 August 2025, the Office for Registration of Medicinal Products (URPL), Poland’s medicines regulator, reiterated that they may be administered only by people licensed to practise as a doctor or a dentist.

Surgical crown lengthening: what does it involve and who is it for?

Surgical crown lengthening is a procedure on the gum and, if needed, also on the bone, which exposes the part of the tooth crown hidden under the gum. A review by Mele et al. (2018) describes its aim as restoring the correct relationship between the gum margin, the crest of the bone and the junction between enamel and root.

The procedure is suited above all to altered passive eruption, when the teeth look short because the gum covers part of them. When the bone is at the correct level, removing the excess gum (gingivectomy) is sometimes enough; when the bone is too close to the edge of the enamel, the dentist also reshapes its margin.

Crown lengthening will not help if the only cause is an overactive lip or excess bone in the upper jaw, which is why diagnosis beforehand matters so much. The procedure is carried out under local anaesthesia, and the dentist discusses how healing goes, the aftercare instructions and the date of the check-up before the procedure.

When is lip repositioning, orthodontics or jaw surgery needed?

Lip repositioning is a procedure that limits how far the upper lip rises when you smile, and it is considered for an overactive or short lip. A review of 13 studies by Mendoza-Geng et al. (2022) reports a reduction in visible gum of an average of 3.06 mm after 6 months, 2.91 mm after 12 months and 2.76 mm after 36 months.

Another review (Dos Santos-Pereira et al., 2021) describes about 25% relapse within the first year and indicates that adding a procedure on the muscle (myotomy) improves the stability of the result. The effect is therefore longer lasting than after toxin, but not always fully permanent.

When a gummy smile results from overerupted incisors with a deep bite, the review by Maleki et al. points to orthodontic treatment with intrusion, that is moving the teeth deeper into the bone. When the cause is vertical maxillary excess, the solution is orthognathic surgery, carried out by a maxillofacial surgeon.

How it works at DentalBlue

At DentalBlue in Białystok, the method is chosen once the cause of the gummy smile has been established. In the clinic’s price list, the item “Uśmiech dziąsłowy” (gummy smile) in the aesthetic medicine category costs 300 zł, and “Chirurgiczne wydłużenie korony” (surgical crown lengthening) in the periodontology category is priced “od 300 zł” (from 300 zł); a periodontal consultation costs 300 zł. The final scope and cost are set at the consultation, and prices may change. When the cause is the position of the teeth, the clinic provides digitally planned orthodontic treatment, with cephalometric analysis from its own radiology unit. A consultation can be arranged by phone.